A crawler crane will be described as an example.
As shown in FIG. 20, a crawler crane includes a crawler-type lower traveling body 1 and an upper rotating body 2 mounted thereon rotatably around a vertical axis.
The upper rotating body 2 includes a rotating frame 3 shown in FIG. 21, which serves as a base. Deck frames (not shown) are attached to both the left and right sides of the rotating frame 3. A boom 4 that can be raised and lowered, three winches (a main winch 5, a subwinch 6, and a boom raising and lowering winch 7), a boom raising and lowering apparatus that raises and lowers the boom 4, and other various necessary pieces of equipment are mounted on the rotating frame 3 and the deck frames.
Many crane models having different lifting capacities are manufactured according to country-specific specifications and standards, specifications required by customers, and so on.
Hitherto, as disclosed in Patent Document 1, rotating frames 3 having different specifications (shapes, sizes, and so on) have been prepared according to individual models, and equipment has been mounted on such a dedicated rotating frame 3 to each model so as to construct an upper rotating body 2.
Specifically, for example, for four models whose lifting capacities are 50 tonnes, 55 tonnes, 65 tonnes, and 80 tonnes, four dedicated rotating frames for 50 tonnes, 55 tonnes, 65 tonnes, and 80 tonnes have been respectively designed and manufactured, and cranes have been assembled on the basis of the rotating frames.
The boom raising and lowering apparatus is selected from two types: a mast apparatus 8 shown in FIG. 20 as a solid line, and a gantry apparatus 9 shown in FIG. 20 as a two-dot chain line and also shown in FIG. 21.
The mast apparatus 8 includes a mast 10. The lower end of the mast 10 is attached to the front of the rotating frame 3. The mast 10 is pivotable around a horizontal axis. A crane can be assembled and disassembled by using the mast apparatus 8 instead of the boom without using another crane. In addition, since the backward protrusion is large, the mast apparatus 8 is suitable for an environment where the rear end radius is not limited. Therefore, the mast apparatus 8 is used mainly outside Japan.
The gantry apparatus 9 is mounted on the rotating frame 3 pivotably with the front and rear lower ends as fulcrums. The gantry apparatus 9 requires an environment where another crane for assembling and disassembling is easily available. In addition, since the backward protrusion is small, the gantry apparatus 9 is suitable for an environment where the rear end radius is limited. Therefore, in Japan, the gantry apparatus 9 is mainly used.
In general, the number of winches is three as described above, and the main winch 5, the subwinch 6, and the boom raising and lowering winch 7 are mounted on the rotating frame 3 in this order from the front at intervals.
In the case of a crane using the gantry apparatus 9, according to the request of the user or the kind of work being performed, separately from the above three standard winches, a third winch 12 (see FIG. 21) for supplementary work can be added as an optional winch. The “third” winch 12 is a winch next to the main winch 5 and the subwinch 6.
In this case, in order to avoid the interference of wire ropes, the main winch 5, the subwinch 6, the third winch 12, and the boom raising and lowering winch 7 are mounted on the rotating frame 3 in this order from the front. That is to say, the three-winch-type boom raising and lowering winch 7 needs to be moved from the third position to the fourth position.
In this case, since the boom raising and lowering winch 7 normally differs from the third winch 12 in size, two types of mounting structure are necessary.
Therefore, the rotating frame 3 needs to be provided with boom-raising-and-lowering-apparatus mounting structures corresponding to the two types of boom raising and lowering apparatuses (the mast apparatus 8 and the gantry apparatus 9), a three-winch-type winch mounting structure, and a four-winch-type winch mounting structure.
That is to say, mounting structures for the following three combinations are necessary:    (i) mast apparatus 8 and three-winch-type winches;    (ii) gantry apparatus 9 and three-winch-type winches; and    (iii) gantry apparatus 9 and four-winch-type winches.
If the standard winches can be replaced with different-sized winches, the types of mounting structure further increase in number.
In FIG. 20, reference numeral 13 designates a rotation bearing for rotatably mounting the upper rotating body 2 on the lower traveling body 1, reference numeral 14 designates a cabin provided on the right-hand side of the front of the upper rotating body 2, reference numeral 15 designates a counterweight provided in the rear of the upper rotating body 2, and reference numeral 16 designates a lifting hook raised and lowered by the main winch 5.    Patent Document 1: Japanese Patent No. 3,436,157